A fifth woman has accused Alabama Senate candidate Roy Moore of sexual misconduct as Republicans increase calls for him to "step aside".

Beverly Young Nelson said she was 16 years old when Mr Moore allegedly tried to force himself on her after offering a ride home from her job as a waitress.

"I tried fight him off while yelling at him to stop," she said, adding that he locked his car to prevent her escape.

Mr Moore, 70, denies the allegations, describing them as a "witch hunt".

But Senator Cory Gardner, the National Republican Senatorial Committee chairman, said on Monday he believes Mr Moore's accusers "spoke with courage and truth" and the former Alabama Supreme Court judge should be expelled if he is elected.

"If he refuses to withdraw and wins, the Senate should vote to expel him, because he does not meet the ethical and moral requirements of the United States Senate," he said.

Mrs Nelson's accusation comes after four other women detailed allegations of sexual misconduct by the conservative firebrand while they were teenagers in Alabama.

The 56-year-old said she met Mr Moore during the late 1970s at the Olde Hickory House restaurant in Gadsen, Alabama, where she worked as a waitress while she was a teenager.

She claimed Mr Moore, a 30-year-old deputy district attorney at the time, offered to sign her high school yearbook and wrote: "To a sweeter more beautiful girl I could not say Merry Christmas."

He signed it "Love, Roy Moore, DA", according to a copy of the yearbook page provided to reporters by her attorney, Gloria Allred.

About a week or two later, he allegedly offered to drive her home and instead drove to the back of the restaurant car park.

"I was terrified. He was also trying to pull my shirt off. I thought he was going to rape me," she told reporters at a news conference on Monday.

"At some point he gave up and he then looked at me and he told me, 'You're just a child,' and he said, 'I am the district attorney of Etowah County. If you tell anyone about this, no one will believe you", Mrs Nelson said, adding that her neck was bruised in the struggle.

"He finally allowed me to open the door and I either fell out or he pushed me out."

"This is a witch hunt against a man who has had an impeccable career for over 30 years and has always been known as a man of high character," he said.

Mr Moore's wife also vehemently denies the allegations, contending that her husband's accusers are being paid.

Earlier on Monday US Senate Republican leader Mitch McConnell said that he believed the women accusing Mr Moore of inappropriate behaviour.

Mr McConnell told reporters in his home state of Kentucky that party officials have considered whether another Republican could challenge Mr Moore in next month's election, through a so-called write-in challenge.

He said Luther Strange, whom Mr Moore beat in the Republican primary earlier this year, was a possible option.

Image copyrightReutersImage caption
Roy Moore said Mitch McConnell is the one who should step aside

Can Republicans ditch Moore?

No matter what happens between now and the 12 December election, Mr Moore's name will remain on the voters' ballot, the Alabama secretary of state has confirmed.

Alabama law prohibits the replacement of a party candidate up to 76 days before the election.

However, voters are free to "write-in" any name they choose and the party might encourage support for another Republican candidate.

The state Republican party could also disqualify Mr Moore's nomination, meaning that if he won the most votes he would still not be declared the winner.

Failing that, if Mr Moore won the election, the US Senate could vote to expel him by arguing that he lacked fitness to serve.

Last week's Washington Post story quoted four women by name, including one who alleged Mr Moore initiated sexual contact with her when she was 14 - beneath the legal age of consent in Alabama - while he was a prosecutor in his 30s.

Mr Moore has said the Washington Post story is a fabricated smear by his political opponents, calling it "a prime example of fake news".

Mr McConnell previously said Mr Moore should step aside only if the allegations were proven true.